1. Field of the Invention
The present invention relates to a mobile node used in a mobile communication system including a plurality of access routers (hereinafter also referred to as “ARaccess router)) for providing a wireless link to a mobile node in a predetermined area, with mobility control being executed based on a mobile IP or its extended system, wherein any one of said access routers provides a wireless link to the mobile node (hereinafter also referred to as “MN” (mobile node)). Furthermore the present invention refers to the aforementioned mobile communication system, a communication control method, and the aforementioned access router.
2. Related Background Art
FIG. 1 is a sequence chart showing operation at the time of handoff of a MN based on non-patent documents 1 and 2 mentioned hereinafter. In FIG. 1, the sequence chart, at the time when a MN has executed handoff from an AR (hereinafter referred to as an oAR (old AR), not shown) to which the MN has been connected until immediately before the handoff to a new AR (hereinafter referred to as an nAR (new AR)) to which the MN has been newly connected, is shown. As shown in FIG. 1, after the handoff (L2 handoff) of the link layer, the MN receives a router advertisement message (2) (hereinafter referred to as RA (router advertisement)) from the nAR. As shown in FIG. 1, in order to receive the RA quickly, the MN can transmit a router solicitation message (1) (hereinafter referred to as RS (router solicitation)) to the nAR.
The MN having received the (2) RA generates a new care of address (hereinafter referred to as nCoA (new care of address)) and transmits a binding update message (3) (hereinafter referred to as BU (binding update)) to a mobility control node (home agent (HA) or mobility anchor point (MAP)). Herewith, the destination is the HA at the mobility control based on the mobile IP and the destination is the MAP at the mobility control based on the hierarchical mobile IP (refer to a non-patent document 3 mentioning later).
The HA or the MAP returns a binding acknowledgement message (4) (hereinafter referred to as BA (binding acknowledgement)) to the BU (3). The nAR having received the (4) BA intends to accomplish routing (transferring), the (4) BA, however, a neighbor cache entry of the nCoA being the destination address does not exist at this moment, so that the nAR can find no MAC address of the nCoA. Therefore, the nAR temporarily stores the BA and inquires the MAC address of a node having the address of the nCoA by transmitting a neighbor solicitation message (5) (hereinafter referred to as NS (neighbor solicitation)).
The MN having received the (5) NS informs the nAR of the MAC address by transmitting a neighbor advertisement message (hereinafter referred to as NA (neighbor advertisement)). The nAR having received the (6) NA generates the neighbor cache entry of the nCoA and transmits the (4) BA, which has been stored temporarily to the MN.
[Non-Patent Document 1] IETF Internet Draft “Mobility Support in IPv6” draft-ietf-mobileip-ipv6-21.txt
[Non-Patent Document 2] IETF RFC2461 “Neighbor Discovery for IP Version 6 (IPv6)”
[Non-Patent Document 3] IETF Internet Draft “Hierarchical Mobile IPv6 mobility management (HMIPv6)” draft-ietf-mobileip-hmipv6-07.txt, October 2002 (work in progress)
[Non-Patent Document 4] IETF RFC2463 “Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification”